1. Field of the Invention
This invention relates to circuit breakers for protecting electric power circuits. More particularly, it relates to circuit breakers with a set of secondary contacts, which are remotely controllable through a latchable operator, such as a magnetically latchable solenoid. The invention also relates to circuit breakers with a set of contacts, which are remotely controllable through a latchable operator.
2. Background Information
Circuit breakers used in residential and light commercial applications are commonly referred to as miniature circuit breakers because of their limited size. Such circuit breakers typically have a pair of separable contacts opened and closed by a spring biased operating mechanism. A thermal-magnetic trip device actuates the operating mechanism to open the separable contacts in response to persistent overcurrent conditions and to short circuits. Usually, circuit breakers of this type for multiple circuits within a residence or commercial structure are mounted together within a load center which may be located in a basement or other remote location. In some applications, it has been found convenient to use the circuit breakers for other purposes than just protection, for instance, for load shedding. It is desirable to be able to perform this function remotely, and even automatically, such as under the control of a computer. However, the spring biased operating mechanisms are designed for manual reclosure and are not easily adapted for reclosing remotely. In any event, such operating mechanisms are not designed for repeated operation over an extended period of time.
U.S. Pat. Nos. 5,301,083 and 5,373,411 describe a remotely operated circuit breaker, which introduces a second pair of contacts in series with the main separable contacts. The main contacts still interrupt the overcurrent, while the secondary contacts perform the discretionary switching operations. The secondary contacts are controlled by a solenoid, which is spring biased to close the contacts. The solenoid has two coils, an opening coil and a holding coil. Initially, both coils are energized to open the contacts. Power to the opening coil is then turned off, and only the holding coil remains energized. Thus, continuous power is required to keep the main contacts open. When power to the holding relay is terminated, the spring recloses the secondary contacts.
There is room for improvement in remotely operated circuit breakers.
There is a need for a remotely controllable circuit breaker, which is simple and economical.
These needs and others are satisfied by the invention, which is directed to a remotely controllable circuit breaker, which includes a latching solenoid to open and close remotely controllable contacts. The solenoid has a coil, which when energized with a first polarity signal, operates the solenoid""s plunger to a first position that opens the contacts, and which when energized with a second polarity signal operates the plunger to a second position in which the contacts are closed.
In accordance with one aspect of the invention, a remotely controllable circuit breaker includes a set of main contacts; an operating mechanism for opening and closing the set of main contacts; a set of secondary contacts electrically connected in series with the set of main contacts, a latching solenoid including a plunger latchable to a first position which opens the set of secondary contacts and to a second position which closes the set of secondary contacts, a coil which when energized with a first polarity signal operates the plunger to the first position and which when energized with an opposite second polarity signal operates the plunger to the second position; and means structured for cooperation with a remote control circuit for energizing the coil with the first polarity signal or, alternatively, the second polarity signal.
The coil may have a first input and a second input; and the means structured for cooperation with a remote control circuit may include: a first terminal, a second terminal electrically connected to the second input of the coil, a switch having a common terminal electrically connected to the first input of the coil, a first switched terminal selectively electrically connectable to the common terminal and a second switched terminal alternatively selectively electrically connectable to the common terminal, a first diode electrically connected between the first switched terminal and the first terminal, and a second diode having an opposite polarity with respect to the first diode electrically connected between the second switched terminal and the first terminal. The remote control circuit may selectively apply the first polarity signal or, alternatively, the second polarity signal between the first and second terminals.
Preferably, the first and second polarity signals are momentary positive and negative DC voltages, respectively.
The switch may have an operating member coupled to the plunger, first contacts electrically connected between the common terminal and the first switched terminal and second contacts electrically connected between the common terminal and the second switched terminal, the first contacts and second contacts being operated by the operating member, with the first contacts being closed when the plunger is in the first position and the second contacts being closed when the plunger is in the second position.
The switch may be a microswitch, and one of the first and second contacts may be a pair of normally closed contacts and the other may be a pair of normally open contacts.
As another aspect of the invention, a remotely controllable circuit breaker comprises: a set of contacts; a latching solenoid including a plunger latchable to a first position which opens the set of contacts and to a second position which closes the set of contacts, a coil which when energized with a first polarity signal operates the plunger to the first position and which when energized with an opposite second polarity signal operates the plunger to the second position; means for providing a trip signal in response to a trip condition of the set of contacts; means cooperating with the means for providing a trip signal for energizing the coil with the first polarity signal in order to open the set of contacts; and means structured for cooperation with a remote control ircuit for alternatively energizing the coil with the second polarity signal in order to lose the set of contacts.
It is an object of the invention to provide a remotely controllable circuit reaker for which remote control circuitry is simple and economical to implement.